Polymeric electrochromics capable of a fast and reversible color change upon electrochemical oxidation and reduction have received a considerable attention over the past decade. A particular emphasis has been placed on incorporating the most stable of these electroactive materials in devices such as windows, mirrors (rear-view/side-view mirrors for cars) and displays, for anticipated industrial and commercial applications. While a number of neutral state red and blue absorbing conjugated polymers have been synthesized and integrated into electrochromic devices, attempts at synthesizing saturated green polymers chemically or electrochemically, which can switch to a transmissive state, have met with limited success due to the complex nature of the required absorption spectrum that must contain at least two bands in the neutral state of the material.
To date, only one article reports the existence of a green conjugated polymer with a transmissive state (with a blue hue) upon oxidation. (Durmus et al., Chem. Commun., 2007, 3246-3248). However, this material is prepared by an electrochemical polymerization/film deposition and does not show any solubility/proccessability making it difficult to be integrated into devices, restricting the scope of possible applications.
Accordingly, soluble neutral state green conjugated polymers with high electrochromic contrasts, fast switching times and highly transmissive oxidized states would be a desirable improvement in the field of conjugated polymers. Additionally, materials that are solution processable would provide advantages in a wide range of applications.